The present invention pertains broadly to bag filters for removal of particulate solids which are entrained in gas stream and pertains more particularly to continuous operation gas filters which are self-cleaning by back-pressuring or reverse flow of a cleaning gas through the walls of the bags.
During continuous operation of a bag filter for removal of entrained solids from a gas stream, a cake of the filtered solids eventually builds up on the walls of the bags and must be periodically removed therefrom lest the bags blind over and become so impermeable as to prevent continued filtration of the gas at a desired rate. Various bag filters have thus been developed whereby gas to be filtered is passed through the wall of the filter bags from the inside to the outside, and a cleaning gas is periodically injected into the interior of the bags to create a pressure therein which is higher than exists in the filter chamber which contains the bags, thereby causing the bags to flex outward and effecting flow of a gas through the walls thereof in a direction in reverse to that in which the gas being filtered normally flows through the walls, thus dislodging accumulated filter cake therefrom.
Exemplary versions of reverse flow, self-cleaning bag filters as have just been broadly described are disclosed in U.S. Pat. Nos. 2,974,478; 3,277,633; 3,487,609; 3,648,442 and 3,793,811. While each of the filters disclosed and claimed in these patents represents a noteworthy advancement in the state of the bag filtering art, they nonetheless suffer the disadvantage of requiring equipment which is complicated and expensive to install and/or operate for supplying cleaning gas to the filter bags, e.g. gas compressors, solenoid valves, electrical controls, moving gas manifolds, chain drivers, mechanical gas valves, etc.
One principal object of the present invention is, therefore, to provide a self-cleaning bag filter of the reverse flow type whereby the aforesaid disadvantages are avoided.
Another object is to provide a self-cleaning, reverse flow bag filter having a greatly simplified and compact means for intermittent reverse flow of a cleaning gas to the filter bags.
Still another object is to provide a self-cleaning, reverse flow bag filter having means for intermittent reverse flow of cleaning gas to the filter bags whereby a quick thrust of pressurized cleaning gas is intermittently supplied to the bags to that they are rapidly flexed outward and also whereby the thrust is retained for a preestablished interval of time to allow reverse passage of cleaning gas through the walls of the bags for separation of particles from the exterior surfaces thereof.
Yet another object is to provide a self-cleaning bag filter of the reverse flow type which is equipped with a plurality of plenum chambers, with filtered gas normally being fed into each plenum chamber from at least one filter bag, and wherein cleaning gas is intermittently charged into each plenum chamber to momentarily generate a pressure therein which is greater than that which exists in the filter chamber that contains the bags.
Other objects and advantages of the present invention will become apparent from the following description and the appended claims.